Where to Put the N-G Bond

[charlie b]

I am doing a peer review. The design includes a detail for transformer connections. It shows the A, B, C, and N wires and "a fifth wire" running from the transformer to the downstream panel. It does not show an N-G bond internal to the transformer, nor internal to the downstream panel. Instead, that "fifth wire" is shown running from the neutral bar internal to the transformer to the ground bar internal to the downstream panel. Although this appears to accomplish what needs to be accomplished, I am not sure it is legal. I also don't know what to call this wire, nor how to size it. Ideas, anyone?

 

[jap]

Charlie you really need to start doing your own electrical designs instead of reviewing others.
Your ideas usually seem to be much more practical than what you review.

JAP>

 

[infinity]

Would it be a SSBJ?

 

[charlie b]

Rob, you are right. It's an SSBJ. It is just that something did not look right to me. And it turns out that something was not right. What the design is missing is the system bonding jumper between the transformer's neutral bar and the transformer enclosure.

 

[infinity]

Rob, you are right. It's an SSBJ. It is just that something did not look right to me. And it turns out that something was not right. What the design is missing is the system bonding jumper between the transformer's neutral bar and the transformer enclosure.

That's what I figured, let's hope that the installer would know to install one even if it weren't on any drawing. FWIW the drawings that we use almost never show the system bonding jumper.

 

[mwm1752]

I know its a choice of design but what advantage does the 5th wire have?

are they calling for a metal raceway between Trans & Panel trying to eliminate parallel paths??

seems simple to not install & bond neutral & electrode system at panel

 

[david luchini]

I know its a choice of design but what advantage does the 5th wire have?

are they calling for a metal raceway between Trans & Panel trying to eliminate parallel paths??

seems simple to not install & bond neutral & electrode system at panel

Making the system bonding jumper connection at the panel doesn't remove the requirement to install the SSBJ. (At least not since the 2011 Code)

 

[kwired]

I know its a choice of design but what advantage does the 5th wire have?

are they calling for a metal raceway between Trans & Panel trying to eliminate parallel paths??

seems simple to not install & bond neutral & electrode system at panel

If the bonding jumper is at the first disconnect you still need a SSBJ back to the transformer case.

 

[Smart $]

... that "fifth wire" is shown running from the neutral bar internal to the transformer to the ground bar internal to the downstream panel. ... I am not sure it is legal. ...

Would it be a SSBJ?

Rob, you are right. It's an SSBJ. It is just that something did not look right to me. And it turns out that something was not right. What the design is missing is the system bonding jumper between the transformer's neutral bar and the transformer enclosure.

What is not legal is the connection of the SSBJ to thetransformer neutral bar. The SSBJ must connect to the end of the SBJ opposite the grounded conductor, i.e. the EGC side. See 250.30(A)(1)(a).

 

[mwm1752]

Making the system bonding jumper connection at the panel doesn't remove the requirement to install the SSBJ. (At least not since the 2011 Code)

If the bonding jumper is at the first disconnect you still need a SSBJ back to the transformer case.

I don't believe that was my question --

 

[Smart $]

I know its a choice of design but what advantage does the 5th wire have?

are they calling for a metal raceway between Trans & Panel trying to eliminate parallel paths??

seems simple to not install & bond neutral & electrode system at panel

I don't believe that was my question --

To answer your question, it is simply a grounding conductor... and yes it must be installed so as not to create a parallel grounded conductor current pathway. Current Code excepts running an SSBJ where there are no "external" metal pathways and an SBJ is installed at both the transformer and the first disconnecting means.

 

[david luchini]

I don't believe that was my question --

I was responding to these statements.

I know its a choice of design

seems simple to not install & bond neutral & electrode system at panel

It is not a design choice. It is Code requirement to install the SSBJ.

 

[ActionDave]

....
seems simple to not install & bond neutral & electrode system at panel

I always bond in the panel. It was the way I was taught and I also think it's easier.

 

[mwm1752]

David - Is that how you read code too lol part of a sentence & not grasp the meaning -- the design is a choice of the engineer to run a fitfh wire or not what was a simple question of what is the advantage to installing the EGC or not has certainly gotten altered. Thought there might be some interesting opinion out there. so sorry to confuse

 

[david luchini]

David - Is that how you read code too lol part of a sentence & not grasp the meaning -- the design is a choice of the engineer to run a fitfh wire or not what was a simple question of what is the advantage to installing the EGC or not has certainly gotten altered. Thought there might be some interesting opinion out there. so sorry to confuse

I'm sorry, but I'm still not following you:?.

There is no "design choice" as whether or not to follow the Code requirements. I've reread your post several times and it still suggests to me that you think installing an SSBJ is a choice, and it would be simpler to not install the SSBJ and just bond the neutral at the panel.

 

[don_resqcapt19]

David - Is that how you read code too lol part of a sentence & not grasp the meaning -- the design is a choice of the engineer to run a fitfh wire or not what was a simple question of what is the advantage to installing the EGC or not has certainly gotten altered. Thought there might be some interesting opinion out there. so sorry to confuse

I don't see what Dave's comment has to do with a "fifth wire". His comment is only about the location of the system bonding jumper.

 

[electrofelon]

I am doing a peer review. The design includes a detail for transformer connections. It shows the A, B, C, and N wires and "a fifth wire" running from the transformer to the downstream panel. It does not show an N-G bond internal to the transformer, nor internal to the downstream panel. Instead, that "fifth wire" is shown running from the neutral bar internal to the transformer to the ground bar internal to the downstream panel. Although this appears to accomplish what needs to be accomplished, I am not sure it is legal. I also don't know what to call this wire, nor how to size it. Ideas, anyone?

sounds to me like it is a system bonding jumper that does not "remain within the same enclosure where it originates" per 250.30(A)(1). Also, depending on the details of the raceway, there may not be a SSBJ.

 

[roger]

seems simple to not install & bond neutral & electrode system at panel

It seems you are thinking Service verses SDS.

Roger

 

[kwired]

I don't believe that was my question --

I may not understand what the question is then.

There needs to be a SSBJ, there is basically two choices of where to make that bond. There needs to be an EGC. How SSBJ is installed has some impact on how EGC originates. EGC could potentially be metallic raceway, which would leave you with only needing "4 wires" in that case, but you still have "5 conductors".

 

[don_resqcapt19]

I may not understand what the question is then.

There needs to be a SSBJ, there is basically two choices of where to make that bond. There needs to be an EGC. How SSBJ is installed has some impact on how EGC originates. EGC could potentially be metallic raceway, which would leave you with only needing "4 wires" in that case, but you still have "5 conductors".

The raceway from the transformer to the panel is not and does not contain an EGC. No mater where the supply side bonding jumper is installed, you need a supply side bonding jumper between the transformer and the panel. The SSBJ can be a non-flexible metallic raceway or a wire.
In either case the EGCs originate in the panel with their associated circuit conductors.

The text in bold should read "system bonding jumper".